Need Direction. Shop Filtration & Ventilation

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Forum topic by apehl posted 07-18-2016 08:06 PM 774 views 0 times favorited 6 replies Add to Favorites Watch
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51 posts in 822 days

07-18-2016 08:06 PM

Topic tags/keywords: resource question

I am new to this form and a novice to woodworking. My shop is an older detached 1 stall garage that holds both my wife’s car and my tools. I live in Iowa and it gets extremely humid in the summer. It is an open span attic and the ventilation is bad. I dont have dust collection system because of the size of my space. I would like to build a shop filtration system using a furnace blower and filters to help with the dust. I also need to get the air moving and ventilated to help with the stale humid air. Can anyone give me suggestions?? My initial thought was to make the unit and vent it through the gables to kill 2 birds with 1 stone. Is this a wise decision? Any help would be greatly appreciated!

6 replies so far

View Fred Hargis's profile

Fred Hargis

5094 posts in 2638 days

#1 posted 07-18-2016 08:29 PM

Well, it seems like if you vent it through the gables, you won’t need any filtration. The vented air might take the dust along with the stale humid air with it. I’m thinking that might not be the case, though. I suspect the dust will be in the lower third of the area, and the stale air in the upper part, the humidity will probably be evenly distributed. So your gable mounted fan would get the upper air, and not as much of the dust (just a guess). You could try it, and if that doesn’t work change things around. Better (maybe) would be to get a regular gable fan for the venting, and have the furnace blower set up with filters to clean the air at a somewhat lower level.

-- Our village hasn't lost it's idiot, he was elected to congress.

View McFly's profile


273 posts in 1172 days

#2 posted 07-18-2016 08:54 PM

Take a look at how your prevailing winds line up with the shop’s orientation, then add fans at each end with one blowing in and another blowing out in the same direction as your prevailing winds.
This should give you the best crossflow for the upper air.

As for cleaning the dirty down low air, can you collect at the machines, then vent to the outside and collect it out there?
This would probably save you the most floor space in what I’m sure is an already tough shop to find square footage.

As for the furnace motor, I figure any interior air filtration can’t hurt; why not have the furnace motor vent clean air right back into the shop?

View clin's profile


929 posts in 1141 days

#3 posted 07-19-2016 03:27 AM

I do think you are talking about two different things. No reason I can think of to filter exterior air used to vent the shop, either coming in or going out.

You want some cross ventilation, not just gable to gable which just has all the fresh air passing over your head. You could still use the gables, but would need to build a duct from near floor height up to one of them.

Do that well (cross ventilation) and there would be no need for any other filtration. But you won’t be wanting to vent like that in January in Iowa, so a room filter is a good idea. Straight forward enough to make yourself. But I would encourage you to get it down to at least a 1 um size filtration. That will require two stages. The first wold be like a typical furnace filter. gets the big stuff you can see. Then the very fine filter to get out the stuff that is really bad for your lungs.

The first stage filter could get clogged making one good sized project (like building a desk). Of course this depends a lot on what you do, how good any other dust collection is so on and so forth. The finer filter may go a long time before it needs replacing or cleaning.

-- Clin

View JeffP's profile


573 posts in 1536 days

#4 posted 07-19-2016 11:10 AM

Welcome to the forum Aphel. This whole air-quality thing is one of the biggest topics here. There are several ways to go and they are often used in combination.

You have several good replies above, and no doubt there will be several more.

One thing I think I can do here is to educate you a bit about the “flavor” of the opinions on this topic.

As with many things in life, there are two extremes on this topic. For air-quality, those extremes are basically “try to hold your breath while making particularly dusty cuts”on the low end, up to “you can’t do proper air-quality in a wood shop without spending thousands of dollars on a 5 HP cyclone dust collector and half-micron can filters” at the other extreme.

Something that I think often goes unnoticed is that there are lots of in-expensive solutions which, while not good enough to satisfy OSHA, and therefore not good enough for a business that has employees, etc. —can still vastly improve the air quality in your hobby shop.

You’re on the right path for such solutions, by looking primarily at moving the dusty air out of your shop rather than trying to filter it.

You should also probably be looking at filter masks as your first line of defense. These two directions can work well together, by using the mask while making dust and for an appropriate amount of time following dust making. The air exchange solutions can greatly increase the speed with which the shop becomes safe again after making a series of cuts or sanding etc. By doing that, the uncomfortable mask-wearing time goes way down.

Even something as simple as placing a couple of $20 box fans near the garage door can quickly move most of the dusty air outside.

-- Last week I finally got my $*i# together. Unfortunately, it was in my shop, so I will probably never find it again.

View brtech's profile


1042 posts in 3067 days

#5 posted 07-19-2016 11:36 AM

Following up on JeffP, I’m one of the “you can’t do proper air-quality in a wood shop without a 5HP cyclone and a half micron filter” guys. The rest of them are in the “hold your hands over your ears and hum loudly” camp, because the facts are that you can’t get the nasty stuff out of the air without a minimum air flow and a minimum filter, and no one really disputes the numbers. They just argue that if you can’t afford it, do whatever you can afford and live with the consequences. The guy with the most facts is Bill Pentz.

JeffP also gives you the basic good advice that if you don’t have said 5HP and 1/2 micron, then use a mask. That works if you use it consistently, you have a good mask that fits well, and you change the filters appropriately. It’s very cheap, very effective, very simple protection. Whenever you make sawdust, wear your mask.

When you move air, your safety goal is get the dust laden air out of the shop before it gets in your lungs. Your assumption is it’s already in the air, and if you breath it, it’s bad for you. But of course, if you aren’t wearing a mask, you do breath it in, and so free air moving and (and filtering) is good, but not safe.

Filtration on air movers actually can do one or both of two things: avoid dust settling on surfaces and get bad stuff out before it gets in your lungs. The latter is impossible (see above), wear a mask. The former is fairly easy to accomplish, and you are heading in the right direction. You want to move as much air as possible, and filter it effectively. Work out a circulation pattern: where the air enters, how you make it move where you want it to go, where it picks up the dust, where you filter it out, and where the air ends up.

If you don’t condition the air (heat or A/C), then you are much better exhausting it than filtering and recycling it. Pull in fresh air, move it past the equipment, and get it out of the shop as directly as you can. If you do condition the air, then you usually can’t afford to exhaust it, you have to recycle it, and then filtration matters more.

If you are filtering, you might as well do as best you can. You can get 20×25 MERV-11 filters pretty cheap. They won’t do anywhere near as good as a Wynn NANO, but they will do much better than the garden variety MERV-8 cheapos that you find in the hardware store. Change them every month or three.

Wear your mask (did I say that before?)

View Jim Finn's profile

Jim Finn

2680 posts in 3067 days

#6 posted 07-23-2016 01:27 AM

I have a $200 filter/fan hanging from my ceiling and it cleans up all the airborne dust in about six minutes in my 300 square feet shop. Mine is a Grizzly. I have had it for about six years now.

-- No PHD just a DD214 Website>

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